The nervous system is the center of nerve messages and the most important regulatory system of the body: it organizes and coordinates vital actions. But it has only two main functions: stimulating muscles to make movements and regulating the functioning of the body, as well as the endocrine system.

The nervous system is divided into the central nervous system and the peripheral nervous system.

In terms of functionality, the nervous system can be divided into somatic (controlling voluntary actions) and autonomic or autonomic (coordinating involuntary actions) systems.

central nervous system

Includes spinal cord and brain. Cognitive and emotional functions of a person are coordinated here. From here all movements are controlled and the weight of feeling is developed.

Brain

In an adult, the brain is one of the heaviest organs of the body: it weighs approximately 1300 g.

It is the center of interaction of the nervous system, and its main function is the transmission of received nerve impulses and the response to them. In its various areas, it mediates the processes of respiration, the solution of specific problems and hunger.

The brain is divided structurally and functionally into several main parts:

Spinal cord

It is located in the spinal canal and is surrounded by the meninges, protecting it from injury. In an adult, the length of the spinal cord reaches 42-45 cm and stretches from the elongated brain (or the inner part of the brain stem) to the second lumbar vertebra and has a different diameter in different parts of the spine.

31 pairs of peripheral spinal nerves depart from the spinal cord, which connect it with the entire body. Its most important function is to connect the various parts of the body with the brain.

Both the brain and the spinal cord are protected by three layers of connective tissue. Between the most superficial and middle layers is a cavity where a fluid circulates, which, in addition to being protected, also nourishes and cleanses the nerve tissues.

Peripheral nervous system

Consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves. It constitutes an intricate network that forms nervous tissue that is not part of the central nervous system and is represented mainly by peripheral nerves responsible for muscles and internal organs.

cranial nerves

12 pairs of cranial nerves leave the brain and pass through the openings of the skull.

All cranial nerves are located in the head and neck, with the exception of the tenth nerve (vagus), which also captures various structures of the chest and stomach.

spinal nerves

Each of the 31 pairs of nerves originates in the dorsal M03IC and continues through the intervertebral foramen. Their names are associated with the place where they originate: 8 cervical, 12 thoracic, 5 lumbar, 5 cross and 1 coccygeal. After passing through the intervertebral foramen, each will be redistributed into 2 branches: the anterior, large, which extends into the distance to cover the muscles and skin in front and sides and the skin of the limbs, and the posterior, smaller, which covers the muscles and skin of the back. The spinal pectoral nerves also communicate with the sympathetic part of the autonomic nervous system. Above in the neck, the roots of these nerves are very short and horizontal.

About that, a person learns in his school years. Biology lessons provide general information about the body in general and about individual organs in particular. As part of the school curriculum, children learn that the normal functioning of the body depends on the state of the nervous system. When failures occur in it, the work of other organs is disrupted. There are various factors that, to one degree or another, influence. nervous system characterized as one of the most important parts of the body. It determines the functional unity of the internal structures of a person and the connection of the organism with the external environment. Let's take a closer look at what is

Structure

To understand what the nervous system is, it is necessary to study all its elements separately. The neuron acts as a structural unit. It is a cell with processes. Circuits are formed from neurons. Speaking about what the nervous system is, it should also be said that it consists of two sections: central and peripheral. The first includes the spinal cord and brain, the second - the nerves and nodes extending from them. Conventionally, the nervous system is divided into autonomic and somatic.

Cells

They are divided into 2 large groups: afferent and efferent. The activity of the nervous system starts with receptors. They perceive light, sound, smells. Efferent - motor - cells generate and direct impulses to certain organs. They consist of a body and a nucleus, numerous processes called dendrites. In isolated fiber - axon. Its length can be 1-1.5 mm. Axons provide the transmission of impulses. In the cell membranes responsible for the perception of smell and taste, there are special compounds. They react to certain substances by changing their state.

Vegetative department

The activity of the nervous system provides the work of internal organs, glands, lymphatic and blood vessels. To a certain extent, it also determines the functioning of the muscles. AT vegetative system allocate parasympathetic and sympathetic divisions. The latter provides for the expansion of the pupil and small bronchi, increased pressure, increased heart rate, etc. The parasympathetic department is responsible for the functioning of the genitals, bladder, and rectum. Impulses emanate from it, activating other glossopharyngeal, for example). The centers are located in the trunk of the head and sacral part of the spinal cord.

Pathologies

Diseases of the autonomic system can be caused by various factors. Quite often, disorders are the result of other pathologies, such as TBI, poisoning, infections. Failures in the vegetative system can be caused by a lack of vitamins, frequent stress. Often diseases are "masked" by other pathologies. For example, if the functioning of the thoracic or cervical nodes of the trunk is disturbed, pain in the sternum is noted, radiating to the shoulder. Such symptoms are characteristic of heart disease, so patients often confuse the pathology.

Spinal cord

Outwardly, it resembles a heavy. The length of this section in an adult is about 41-45 cm. There are two thickenings in the spinal cord: lumbar and cervical. They form the so-called innervation structures of the lower and upper limbs. In the following departments are distinguished: sacral, lumbar, thoracic, cervical. Throughout its length, it is covered with soft, hard and arachnoid shells.

Brain

It is located in the cranium. The brain consists of the right and left hemispheres, brainstem and cerebellum. It has been established that its weight in men is greater than in women. The brain begins its development in the embryonic period. The body reaches its real size by about 20 years. By the end of life, the weight of the brain decreases. It has departments:

1. Finite.
2. Intermediate.
3. Average.
4. Rear.
5. Oblong.

hemispheres

They also have an olfactory center. The outer shell of the hemispheres has a rather complex pattern. This is due to the presence of ridges and furrows. They form a kind of "convolutions". Each person has a unique drawing. However, there are several furrows that are the same for everyone. They allow you to distinguish five lobes: frontal, parietal, occipital, temporal and hidden.

Unconditioned reflexes

Nervous system processes- response to stimuli. Unconditioned reflexes were studied by such a prominent Russian scientist as IP Pavlov. These reactions are focused mainly on the self-preservation of the organism. The main ones are food, orientation, defensive. Unconditioned reflexes are innate.

Classification

Unconditioned reflexes were studied by Simonov. The scientist singled out 3 classes of innate reactions corresponding to the development of a particular area of ​​the environment:

Orienting reflex

It is expressed in involuntary sensory attention, accompanied by an increase in muscle tone. A reflex is evoked by a new or unexpected stimulus. Scientists call this reaction "alarming", anxiety, surprise. There are three phases of its development:

1. Cessation of current activity, fixation of posture. Simonov calls this general (preventive) inhibition. It occurs on the appearance of any stimulus with an unknown signal.
2. Transition to the "activation" reaction. At this stage, the body is transferred to a reflex readiness for a likely meeting with an emergency. This is manifested in a general increase in muscle tone. In this phase, a multicomponent reaction takes place. It includes turning the head, eyes towards the stimulus.
3. Fixation of the stimulus field to start a differentiated analysis of signals and select a response.

Meaning

The orienting reflex is included in the structure of exploratory behavior. This is especially evident in the new environment. Research activities can be focused on both the development of novelty and the search for an object that can satisfy curiosity. In addition, it can also provide an analysis of the significance of the stimulus. In such a situation, an increase in the sensitivity of the analyzers is noted.

Mechanism

The implementation of the orienting reflex is a consequence of the dynamic interaction of many formations of nonspecific and specific elements of the CNS. The general activation phase, for example, is associated with the initiation and onset of generalized cortical excitation. When analyzing the stimulus, cortical-limbic-thalamic integration is of primary importance. The hippocampus plays an important role in this.

Conditioned reflexes

At the turn of the 19th-20th centuries. Pavlov, who studied the work of the digestive glands for a long time, revealed the following phenomenon in experimental animals. An increase in the secretion of gastric juice and saliva occurred regularly, not only when food directly entered the gastrointestinal tract, but also while waiting for it to be received. At that time, the mechanism of this phenomenon was not known. Scientists explained it by "mental stimulation" of the glands. In the course of subsequent research, Pavlov attributed such a reaction to conditioned (acquired) reflexes. They can come and go over the course of a person's life. For a conditioned response to occur, two stimuli must coincide. One of them in any conditions provokes a natural response - without conditioned reflex. The second, due to its routine, does not provoke any reaction. It is defined as indifferent (indifferent). In order for a conditioned reflex to arise, the second stimulus must begin to act earlier than the unconditioned reflex by a few seconds. At the same time, the biological significance of the former should be less.

Nervous system protection

As you know, a variety of factors affect the body. State of the nervous system affects other organs. Even seemingly minor failures can cause serious illness. At the same time, they will not always be associated with the activity of the nervous system. In this regard, much attention should be paid to preventive measures. First of all, it is necessary to reduce irritating factors. It is known that constant stress, experiences are one of the causes of cardiac pathologies. The treatment of these diseases includes not only medicines, but also physiotherapy, exercise therapy, etc. Diet is of particular importance. The state of all human systems and organs depends on proper nutrition. Food should contain enough vitamins. Experts recommend including plant foods, herbs, vegetables and fruits in the diet.

Vitamin C

It has a beneficial effect on all body systems, including the nervous system. Vitamin C provides energy at the cellular level. This compound is involved in the synthesis of ATP (adenosine triphosphoric acid). Vitamin C is considered one of the strongest antioxidants, it neutralizes the negative effects of free radicals by binding them. In addition, the substance is able to enhance the activity of other antioxidants. These include vitamin E and selenium.

Lecithin

It ensures the normal course of processes in the nervous system. Lecithin is the main nutrient for cells. The content in the peripheral section is about 17%, in the brain - 30%. With insufficient intake of lecithin, nervous exhaustion occurs. The person becomes irritable, which often leads to nervous breakdowns. Lecithin is necessary for all cells of the body. It is included in the B-vitamin group and promotes energy production. In addition, lecithin is involved in the production of acetylcholine.

Music that calms the nervous system

As mentioned above, in diseases of the central nervous system, therapeutic measures may include not only taking medications. The therapeutic course is selected depending on the severity of the violations. Meanwhile, relaxation of the nervous system often achieved without consulting a doctor. A person can independently find ways to relieve irritation. For example, there are different melodies. As a rule, these are slow compositions, often without words. However, a march can also calm some people. When choosing melodies, you should focus on your own preferences. You just need to make sure that the music is not depressing. Today, a special relaxing genre has become quite popular. It combines classical, folk melodies. The main sign of relaxing music is a quiet monotony. It "envelops" the listener, creating a soft but strong "cocoon" that protects the person from external irritations. Relaxing music can be classical, but not symphonic. Usually it is performed by one instrument: piano, guitar, violin, flute. It can also be a song with repeated recitative and simple words.

The sounds of nature are very popular - the rustle of leaves, the sound of rain, bird singing. In combination with the melody of several instruments, they take a person away from the daily hustle and bustle, the rhythm of the metropolis, relieve nervous and muscular tension. When listening, thoughts are ordered, excitement is replaced by calmness.

The nervous system is an integral morphological and functional set of various interconnected nervous structures, which, together with the humoral system, provides an interconnected regulation of the activity of all body systems and a reaction to changing conditions of the internal and external environment. The nervous system consists of neurons, or nerve cells, and neuroglial cells (neuroglia). Neurons are the main structural and functional elements in both the central and peripheral nervous systems. Neurons- These are excitable cells, that is, they are able to generate and transmit electrical impulses (action potentials). Neurons have different shapes and sizes, form processes of two types: axons and dendrites. A neuron usually has several short branched dendrites, along which impulses follow to the body of the neuron, and one long axon, along which impulses go from the body of the neuron to other cells (neurons, muscle or glandular cells). The transfer of excitation from one neuron to other cells occurs through specialized contacts - synapses. neuroglial cells are more numerous than neurons and make up at least half the volume of the central nervous system, but unlike neurons they cannot generate action potentials. Neuroglial cells are different in structure and origin, they perform auxiliary functions in the nervous system, providing support, trophic, secretory, delimiting and protective functions. According to their functional purpose, they distinguish 1) somatic or animal nervous system, 2) autonomic or autonomic nervous system.

In turn, in the autonomic nervous system, there are:

• Sympathetic division of the autonomic nervous system
• Parasympathetic division of the autonomic nervous system
• Metasympathetic division of the autonomic nervous system (enteric nervous system).

Central nervous system (CNS) - the main part of the nervous system of animals and humans, consisting of an accumulation of nerve cells (neurons) and their processes; it is represented in invertebrates by a system of closely interconnected nerve nodes (ganglia), in vertebrates and humans - by the spinal cord and brain.

The main and specific function of the central nervous system is the implementation of simple and complex highly differentiated reflective reactions, called. In higher animals and humans, the lower and middle sections of the central nervous system - the spinal cord, medulla oblongata, midbrain, diencephalon and cerebellum - regulate the activity of individual organs and systems of a highly developed organism, communicate and interact between them, ensure the unity of the organism and the integrity of its activity. The highest department of the central nervous system - the cerebral cortex and the nearest subcortical formations - mainly regulates the connection and relationship of the body as a whole with the environment.

The central nervous system is connected with all organs and tissues through the peripheral nervous system, which in vertebrates includes cranial nerves extending from the brain, and spinal nerves - from the spinal cord, intervertebral nerve nodes, as well as the peripheral part of the autonomic nervous system - nerve nodes, with suitable to him (preganglionic) and departing from them (postganglionic) nerve fibers. Sensitive, or afferent, nerve adductor fibers carry excitation to the central nervous system from peripheral receptors; along the efferent efferent (motor and autonomic) nerve fibers, excitation from the central nervous system is directed to the cells of the executive working apparatus (muscles, glands, blood vessels, etc.). In all parts of the CNS there are afferent neurons that perceive stimuli coming from the periphery, and efferent neurons that send nerve impulses to the periphery to various executive organs. Afferent and efferent cells, with their processes, can contact each other and form a two-neuron reflex arc that performs elementary reflexes (for example, tendon reflexes of the spinal cord). But, as a rule, interneurons, or interneurons, are located in the reflex arc between the afferent and efferent neurons. Communication between different parts of the CNS is also carried out with the help of many processes of afferent, efferent and intercalary neurons of these parts, which form intracentral short and long pathways. The CNS also includes neuroglial cells, which perform a supporting function in it, and also participate in the metabolism of nerve cells.

The autonomic nervous system is a part of the nervous system that has a two-neuron structure and innervates the internal organs, smooth muscles, heart, endocrine glands and skin;

Through the autonomic nervous system, the central nervous system regulates the functions of internal organs, blood supply and trophism of all organs. The autonomic nervous system is divided into sympathetic and parasympathetic divisions.

The sympathetic nervous system is the peripheral part of the autonomic nervous system, which ensures the mobilization of the body's existing ones to perform urgent work. The sympathetic nervous system stimulates the heart, constricts blood vessels, and enhances the performance of skeletal muscles. The sympathetic nervous system is represented by:

• gray matter of the lateral horns of the spinal cord;
• two symmetrical sympathetic trunks with their ganglia;
• internodal and connecting branches; as well as
• branches and ganglia involved in the formation of nerve plexuses.

Parasympathetic nervous system - the peripheral part of the autonomic nervous system responsible for maintaining constancy internal environment organism. The parasympathetic nervous system consists of:

• the cranial region, in which the preganglionic fibers leave the midbrain and rhomboid brain as part of several cranial nerves; and
• sacral region, in which preganglionic fibers exit the spinal cord as part of its ventral roots.

The parasympathetic nervous system slows down the work of the heart, dilates some blood vessels.

The main directions of research of the nervous system

Modern science of the nervous system combines many scientific disciplines: along with classical neuroanatomy, neurology and neurophysiology, an important contribution to the study of the nervous system is made by molecular biology and genetics, chemistry, cybernetics and a number of other sciences. This interdisciplinary approach to the study of the nervous system is reflected in the term neuroscience. In the Russian-language scientific literature, the term "neurobiology" is often used as a synonym. One of the main goals of neuroscience is to understand the processes occurring both at the level of individual neurons and neural networks, the result of which are various mental processes: thinking, emotions, consciousness.<В соответствие с этой задачей изучение нервной системы ведется на разных уровнях организация, начиная с молекулярного и заканчивая изучением сознания, творческих способностей и социального поведения.

The human nervous system is similar in structure to the nervous system of higher mammals, but differs in a significant development of the brain. The main function of the nervous system is to control the vital activity of the whole organism.

Neuron

All organs of the nervous system are built from nerve cells called neurons. A neuron is capable of receiving and transmitting information in the form of a nerve impulse.

Rice. 1. Structure of a neuron.

The body of a neuron has processes by which it communicates with other cells. The short processes are called dendrites, the long ones are called axons.

The structure of the human nervous system

The main organ of the nervous system is the brain. It is connected to the spinal cord, which looks like a cord about 45 cm long. Together, the spinal cord and brain make up the central nervous system (CNS).

Rice. 2. Scheme of the structure of the nervous system.

Nerves leaving the CNS make up the peripheral part of the nervous system. It consists of nerves and nerve nodes.

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Nerves are formed from axons, the length of which can exceed 1 m.

Nerve endings contact each organ and transmit information about their condition to the central nervous system.

There is also a functional division of the nervous system into somatic and autonomic (autonomous).

The part of the nervous system that innervates the striated muscles is called the somatic. Her work is connected with the conscious efforts of a person.

The autonomic nervous system (ANS) regulates:

• circulation;
• digestion;
• selection;
• breath;
• metabolism;
• smooth muscle work.

Thanks to the work of the autonomic nervous system, there are many processes of normal life that we do not consciously regulate and usually do not notice.

The significance of the functional division of the nervous system is in ensuring the normal, independent of our consciousness, functioning of the finely tuned mechanisms of the work of internal organs.

The highest organ of the ANS is the hypothalamus, located in the intermediate part of the brain.

The ANS is divided into 2 subsystems:

• sympathetic;
• parasympathetic.

Sympathetic nerves activate the organs and control them in situations that require action and increased attention.

Parasympathetic slow down the work of the organs and turn on during rest and relaxation.

For example, sympathetic nerves dilate the pupil, stimulate salivation. Parasympathetic, on the contrary, narrow the pupil, slow down salivation.

Reflex

This is the response of the body to irritation from the external or internal environment.

The main form of activity of the nervous system is a reflex (from the English reflection - reflection).

An example of a reflex is pulling the hand away from a hot object. The nerve ending perceives high temperature and transmits a signal about it to the central nervous system. In the central nervous system, a response impulse arises, going to the muscles of the arm.

Rice. 3. Scheme of the reflex arc.

Sequence: sensory nerve - CNS - motor nerve is called the reflex arc.

Brain

The brain is characterized by a strong development of the cerebral cortex, in which the centers of higher nervous activity are located.

The features of the human brain sharply separated it from the animal world and allowed it to create a rich material and spiritual culture.

What have we learned?

The structure and functions of the human nervous system are similar to those of mammals, but differ in the development of the cerebral cortex with the centers of consciousness, thinking, memory, and speech. The autonomic nervous system controls the body without the participation of consciousness. The somatic nervous system controls the movement of the body. The principle of activity of the nervous system is reflex.

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Nervous system

Responsible for the coordinated activity of various organs and systems, as well as for the regulation of body functions nervous system. It also connects the organism with the external environment, thanks to which we feel various changes in the environment and react to them. The nervous system is divided into central, represented by the spinal cord and brain, and peripheral, which includes nerves and nerve nodes. From the point of view of the regulation process, the nervous system can be divided into somatic, which regulates the activity of all muscles, and vegetative, which controls the coordination of the functioning of the cardiovascular, digestive, excretory systems, endocrine and external secretion glands.

The activity of the nervous system is based on the properties of the nervous tissue - excitability and conductivity. A person reacts to any irritation coming from the external environment. This response of the body to irritation, carried out through the central nervous system, is called reflex, and the path that the excitation goes through is reflex arc.

The spinal cord is like a long cord formed by nervous tissue. It is located in the spinal canal: from above, the spinal cord passes into the medulla oblongata, and below it ends at the level of the 1st-2nd lumbar vertebra. The spinal cord consists of gray and white matter, and in the center of it runs a canal filled with cerebrospinal fluid.

Numerous nerves extending from the spinal cord connect it with internal organs and limbs. The spinal cord performs two functions - reflex and conduction. It connects the brain with the organs of the body, regulates the functioning of the internal organs, ensures the movement of the limbs and trunk, and is under the control of the brain.

The brain is made up of several sections. Usually, the hindbrain (it includes the medulla oblongata connecting the spinal cord and brain, the bridge and the cerebellum), the midbrain and the forebrain, formed by the diencephalon and the cerebral hemispheres, are usually distinguished.

Large hemispheres are the largest part of the brain. Distinguish between right and left hemispheres. They consist of a bark formed by gray matter, the surface of which is dotted with convolutions and furrows, and processes of white matter nerve cells. The processes that distinguish humans from animals are associated with the activity of the cerebral cortex: consciousness, memory, thinking, speech, labor activity. According to the names of the bones of the skull, to which various parts of the cerebral hemispheres adjoin, the brain is divided into lobes: frontal, parietal, occipital and temporal.

A very important part of the brain responsible for the coordination of movements and balance of the body - the cerebellum - is located in the back of the brain above the medulla oblongata. Its surface is characterized by the presence of many folds, convolutions and furrows. In the cerebellum, the middle part and lateral sections are distinguished - the cerebellar hemispheres. The cerebellum is connected to all parts of the brain stem.

The brain controls and directs the work of human organs. So, for example, in medulla oblongata there are respiratory and vasomotor centers. Rapid orientation during light and sound stimuli is provided by centers located in the midbrain. diencephalon participates in the formation of sensations. There are a number of zones in the cerebral cortex: for example, in the musculocutaneous zone, impulses from the receptors of the skin, muscles, and articular bags are perceived, and signals are formed that regulate voluntary movements. In the occipital lobe of the cerebral cortex, there is a visual zone that perceives visual stimuli. The auditory zone is located in the temporal lobe. On the inner surface of the temporal lobe of each hemisphere are the gustatory and olfactory zones. And, finally, in the cerebral cortex there are areas that are peculiar only to humans and are absent in animals. These are the areas that control speech.